The Night of Kadar tells the story of a crew of interplanetary colonists. On their approach to a distant planet, while these human space voyagers were still in a state of suspended animation, an alien life force enters the ship. It investigates and interferes with the minds of the sleeping humans, and also subtly disrupts some of the on-board systems. Upon landing on the planet, the crew experiences confusion and disorientation. Certain elements of the colonization party are missing, and there is no sign of their spacecraft. Eventually one man, Osman, reluctantly takes a position of leadership. He organizes the setup of the colony and the exploration of the world, although he has only a fragment of the manpower and equipment originally assigned to the mission.

An interesting distinction of this novel is in the religion of the crew: they are Moslems. Although they start out as rather secular people, Osman has them build a mosque, encouraging them to adhere to their religious principles. Throughout the novel, a sense of lost heritage and memory continues to gnaw at the colonists, if only in a vague, unsettling way. By embracing their religion, they gain a measure of solace. Although Islam is a relatively minor aspect of Kadar, it does make the novel stand out from the run-of-the-mill science fiction of the 1970s, anticipating by several decades the West's newfound interest in Islam.

As they build a settlement and begin a new life, the colonists meet a variety of native life forms. At first, the creatures seem harmless, almost comical. Soon, however, some enormous, beetle-like creatures do pose a threat. The colonists also have occasional run-ins with a strange, glowing orb that appears and disappears without warning.

Eventually, after a series of travels and adventures, the colonists discover a tribe of fierce, brutish humans. These savages vastly outnumber Osman's people, and eventually overwhelm them. At the end of the novel, Osman and his men learn the awful truth: their assailants are actually the crew of the missing spacecraft. These unfortunates have lost all knowledge of modern technology, and know no better than to turn broken bits of equipment into primitive weapons for slaughter. In the end, the reader learns that all of the tribulations of Osman and his people were machinations of an alien life force. The same being that had disrupted the minds of the crew in the first place has been operating the glowing orb as a kind of mobile, remote monitor. The orb serves to provide an entertaining spectacle to the formless alien that controls it from a location far from the planet where the action takes place. Thus, the novel's conclusion might be considered a deus ex machina. All human striving turns out to be nothing but a puppet show for superior beings, our very existence absurd.